This invention relates to the production of hydrocarbon derivatives by the partial oxidation of hydrocarbons, and more particularly to the use of air separation products in a recycle partial oxidation process.
Certain partial oxidation products are produced commercially by the oxidation of an appropriate hydrocarbon in the vapor phase over a suitable catalyst. For example, maleic anhydride is produced commercially by the vapor phase catalytic partial oxidation of aromatic hydrocarbons, such as benzene, or straight-chain hydrocarbons, such as n-butane or butene, in the presence of an oxygen-containing gas, over a vanadium-containing catalyst. Similarly, nitriles, alkylene oxides, aldehydes and halogenated hydrocarbons are produced by the partial oxidation of appropriate alkanes and alkenes in the presence of selected catalysts. Air has generally been used as the oxygen-containing gas, because of its low cost and ready availability. The reaction can be carried out in any suitable reactor, and the effluent from the reactor generally contains be carried out in any suitable reactor, and the effluent from the reactor generally contains the partial oxidation product, carbon dioxide (CO.sub.2), carbon monoxide (CO), water, unreacted hydrocarbon and smaller amounts of other partially oxidized byproducts.
The reaction equipment train generally consists of a reactor, in which the partial oxidation product is produced, a scrubber, in which the partial oxidation product is scrubbed from the reactor effluent gases by means of water or other solvent for the partial oxidation product, and means for further treating the scrubbed effluent gases. In modem recycle processes means are also provided for removing unreacted hydrocarbons from the scrubbed gas stream and recycling them to the partial oxidation reactor.
Adsorption systems are often used for removing unreacted hydrocarbons from scrubbed partial oxidation gaseous effluents. When used for such purpose the system generally contains an adsorbent which preferentially adsorbs unreacted hydrocarbon from the scrubbed gas stream. When the system is designed properly it adsorbs the unreacted hydrocarbons without also adsorbing excessive amounts of the other components of the gas stream, such as nitrogen, argon, carbon dioxide and carbon monoxide.
When temperature swing adsorption (TSA) systems are used for the removal of the unreacted hydrocarbon from offgas streams from partial oxidation reactors, the adsorption beds are generally regenerated by passing a heated nonadsorbable or weakly adsorbable purge gas through the bed. The purge gas desorbs the adsorbed components from the bed and sweeps them out of the system. U.S. Pat. No. 4,23 1,943 discloses a TSA process for the production of maleic anhydride by the partial oxidation of n-butane. In the process disclosed in this patent a portion of the n-butane-containing off gas from the product gas scrubber is recycled directly to the partial oxidation reactor, and the remainder is passed through an adsorption dram wherein butane is adsorbed from the offgas. The n-butane is desorbed from the adsorption bed by purging the bed with heated nitrogen or a nitrogen-air mixture. The n-butane-purge gas mixture is recycled to the partial oxidation reactor. Federal Republic of Germany Patent Disclosure 25 44 972 likewise discloses a partial oxidation reaction process for producing maleic anhydride in which unreacted C.sub.4 hydrocarbons are recovered from the reactor offgas by temperature swing adosrption. In this patent the adsorption bed is purged with heated air.
The present invention provides a process which provides advantages over the above-described processes.